diff --git a/lecture/yarn.lock b/lecture/yarn.lock
index e906f11..90ee7a4 100644
--- a/lecture/yarn.lock
+++ b/lecture/yarn.lock
@@ -4637,21 +4637,6 @@ node-notifier@^5.0.2:
     shellwords "^0.1.1"
     which "^1.3.0"
 
-node-pre-gyp@*:
-  version "0.14.0"
-  resolved "https://registry.yarnpkg.com/node-pre-gyp/-/node-pre-gyp-0.14.0.tgz#9a0596533b877289bcad4e143982ca3d904ddc83"
-  dependencies:
-    detect-libc "^1.0.2"
-    mkdirp "^0.5.1"
-    needle "^2.2.1"
-    nopt "^4.0.1"
-    npm-packlist "^1.1.6"
-    npmlog "^4.0.2"
-    rc "^1.2.7"
-    rimraf "^2.6.1"
-    semver "^5.3.0"
-    tar "^4.4.2"
-
 node-pre-gyp@^0.12.0:
   version "0.12.0"
   resolved "https://registry.yarnpkg.com/node-pre-gyp/-/node-pre-gyp-0.12.0.tgz#39ba4bb1439da030295f899e3b520b7785766149"
@@ -5021,8 +5006,8 @@ path-key@^2.0.0:
   resolved "https://registry.yarnpkg.com/path-key/-/path-key-2.0.1.tgz#411cadb574c5a140d3a4b1910d40d80cc9f40b40"
 
 path-parse@^1.0.5, path-parse@^1.0.6:
-  version "1.0.6"
-  resolved "https://registry.yarnpkg.com/path-parse/-/path-parse-1.0.6.tgz#d62dbb5679405d72c4737ec58600e9ddcf06d24c"
+  version "1.0.7"
+  resolved "https://registry.yarnpkg.com/path-parse/-/path-parse-1.0.7.tgz#fbc114b60ca42b30d9daf5858e4bd68bbedb6735"
 
 path-to-regexp@0.1.7:
   version "0.1.7"
@@ -5596,14 +5581,14 @@ react-dev-utils@^5.0.2:
     strip-ansi "3.0.1"
     text-table "0.2.0"
 
-react-dom@16.12.0:
-  version "16.12.0"
-  resolved "https://registry.yarnpkg.com/react-dom/-/react-dom-16.12.0.tgz#0da4b714b8d13c2038c9396b54a92baea633fe11"
+react-dom@^16.12.0:
+  version "16.14.0"
+  resolved "https://registry.yarnpkg.com/react-dom/-/react-dom-16.14.0.tgz#7ad838ec29a777fb3c75c3a190f661cf92ab8b89"
   dependencies:
     loose-envify "^1.1.0"
     object-assign "^4.1.1"
     prop-types "^15.6.2"
-    scheduler "^0.18.0"
+    scheduler "^0.19.1"
 
 react-error-overlay@^4.0.1:
   version "4.0.1"
@@ -5658,9 +5643,9 @@ react-scripts@1.1.5:
   optionalDependencies:
     fsevents "^1.1.3"
 
-react@16.12.0:
-  version "16.12.0"
-  resolved "https://registry.yarnpkg.com/react/-/react-16.12.0.tgz#0c0a9c6a142429e3614834d5a778e18aa78a0b83"
+react@^16.12.0:
+  version "16.14.0"
+  resolved "https://registry.yarnpkg.com/react/-/react-16.14.0.tgz#94d776ddd0aaa37da3eda8fc5b6b18a4c9a3114d"
   dependencies:
     loose-envify "^1.1.0"
     object-assign "^4.1.1"
@@ -6050,9 +6035,9 @@ sax@^1.2.1, sax@^1.2.4, sax@~1.2.1:
   version "1.2.4"
   resolved "https://registry.yarnpkg.com/sax/-/sax-1.2.4.tgz#2816234e2378bddc4e5354fab5caa895df7100d9"
 
-scheduler@^0.18.0:
-  version "0.18.0"
-  resolved "https://registry.yarnpkg.com/scheduler/-/scheduler-0.18.0.tgz#5901ad6659bc1d8f3fdaf36eb7a67b0d6746b1c4"
+scheduler@^0.19.1:
+  version "0.19.1"
+  resolved "https://registry.yarnpkg.com/scheduler/-/scheduler-0.19.1.tgz#4f3e2ed2c1a7d65681f4c854fa8c5a1ccb40f196"
   dependencies:
     loose-envify "^1.1.0"
     object-assign "^4.1.1"
@@ -6552,7 +6537,7 @@ tapable@^0.2.7:
   version "0.2.9"
   resolved "https://registry.yarnpkg.com/tapable/-/tapable-0.2.9.tgz#af2d8bbc9b04f74ee17af2b4d9048f807acd18a8"
 
-tar@^4, tar@^4.4.2:
+tar@^4:
   version "4.4.13"
   resolved "https://registry.yarnpkg.com/tar/-/tar-4.4.13.tgz#43b364bc52888d555298637b10d60790254ab525"
   dependencies: