Can you please explain both parts in detail

(a) The sum of integers from 1 to N is N(N+1)/2, that is 1+2+. . .+N = N(N+1)/2. Suppose a programmer does not know this formula and wants to compute the sum of integers from 1 to N. The programmer writes a program by adding 1 and 2 first and then getting the result and adding it with 3, and so on: (((1+2)+3)+. . .+N). Find the running time this will take in terms of N. You should use the big-O notation for running time.

(b) Find the running time in terms of N that it would take you to compute the sum using the formula N(N + 1)/2. Youll see this is much faster.