Find the Riemann sum associated with

Question

f(x)=4x^2+2, n=3 and the partition
xsub0=-2
xsub1=1
xsub2=2
xsub3=4
of [-2,4]
(a) when xsubk is the right end-point of [xsubk-1, xsubk] .

(b) when when xsubk is the mid-point of [xsubk-1, xsubk]

please help. i thought fora the anser was 216 but that's not right and i keep getting that answer so i must be doing something wrong. i thought u have to take the definate integral of the equation given from -2 to 4 and then multiply that by two..please tell me what i am doing wrong and what numbers to use for b...thank you!!