4. Find the convolution of $f(t)=\left\{\begin{array}{11}\frac{3}{2} t, & 9 \leq t \leq 3 110, & \text { otherwise } \end{array} ight. $ and $g(t)=\left\{\begin{array}{11}4, & -1 \leq t \leq 30, & \text { otherwise } \end{array} ight. $ Answer: $$ f*g=\left\{\begin{array}{11} 0 & t \leqslant-1 \frac{4}{3}(t+1)^{2} & -16 \end{array} ight. $$ SP.SD.3301