a manufacturer's cost is given by C= 300 cube root of n + 1200, where c is the cost and n is the number of parts produced. find the cost when 8 parts are produced. help please!!!!

We have C = 300n1/3 +1200
Substitute 8 for n to get
C = 300*81/3 +1200
You should know that 23=8, so what is 81/3?