Expectation of runtime

Question

I am running a program and its runtime follows a normal distribution $T_i = N(t,\sigma).$ Now, I am running $n$ programs in parallel ($T_1, T_2, \cdots, T_n$ are i.i.d.), and the finish time for $n$ program is finished when the last one finished - $T' = \max(T_1, T_2, T_3,\cdots, T_n)$. What is the expectation for $T'$? I am asking this because I encounter this problem in my computational works.