Answer: It seems like there might be a mistake in the expression you provided. The variable "n" is not defined, and it does not appear in the summation. It seems like you might have meant to write:
s4 = 4∑k=1 2(3k-1)
Assuming that this is the correct expression, we can evaluate it as follows:
s4 = 4∑k=1 2(3k-1)
= 4 * [2(3(1)-1) + 2(3(2)-1) + 2(3(3)-1) + 2(3(4)-1)]
= 4 * [2(2) + 2(5) + 2(8) + 2(11)]
= 4 * [4 + 10 + 16 + 22]
= 4 * 52
= 208
Therefore, s4 = 208.