Please correctly and handwritten

From February $1972$ to February $1975,10$ severe viral hepatitis patients from various hospitals in California were placed on steroids therapy. The survival times were

$1,1,3,4,7,8,8,10+,14+,15+,$

where the symbol $"+"$ represents a censored observation. Assume that survival times are exponentially distributed $S(t)=e^{-t}.$

A$)$ Compute ${\displaystyle \underset{i=1}{\overset{n}{}}}{}_i.$

B$)$ Compute ${\displaystyle \underset{i=1}{\overset{n}{}}}{t}_i.$

C$)$ Estimate $$ by maximum likelihood.