Let $t$ be TNYWR.

What is the area of a triangle with base of length $2 t$ and height of length $3 t+1$ ?
The area of a triangle with base of length $2 t$ and height of length $3 t+1$ is $\frac{1}{2}(2 t)(3 t+1)$ or $t(3 t+1)$.

Since the answer to (a) is 4 , then $t=4$, and so $t(3 t+1)=4(13)=52$.