fix R8a and add R8*.md and build them

reviews/R8d.md

@@ -0,0 +1,43 @@
+# Review 8-4
+
+* Hajin Ju, 2024062806
+
+## Problem 1
+
+What is the dimension of the matrix product $AB$ if $A$ is a $p\times q$ matrix and $B$ is a $q\times r$ matrix?
+
+### Solution 1
+
+$p\times r$
+
+## Problem 2
+
+Count the number of scalar multiplications to multiply $A$ and $B$ where $A$ is a $p\times q$ matrix and $B$ is a $q\times r$ matrix.
+
+### Solution 2
+
+$pqr$
+
+## Problem 3
+
+Count the number of scalar multiplications where the dimensions of $A_1$, $A_2$, and $A_3$$ are $10\times 100$, $100\times 5$ and $5\times 50$, respectively.
+
+1. $(A_1A_2)A_3$
+2. $A_1(A_2A_3)$
+
+### Solution 3
+
+1. $5000 + 2500 = 7500$
+2. $25000 + 50000 = 75000$
+
+## Problem 4
+
+Fully parenthesize the product $A_1A_2A_3A_4$. (There are five distinct ways.)
+
+### Solution 4
+
+1. $(A_1A_2)(A_3A_4)$
+2. $(A_1(A_2A_3))A_4$
+3. $A_1(A_2(A_3A_4))$
+4. $A_1((A_2A_3)A_4)$
+5. $((A_1A_2)A_3)A_4$