Qbasic help, please

im sure theres somebody out there that this will be rediculously easy to. please help me, i cant figure this shit out.

~ construct a top-down program to find the mean(m), the variance (v), and the standard deviation (sd) of a variable number of student grades (g1, g2, g3,......, gn). use the following three formulas
M = ( g1 + g2 + g3 + ..... + gn) / n
v = [(g1-m)^2 + ..... (gn - m)^2] / (n-1)
sd = square root of v

where n is the total number of grades

use READ and DATA statements for the student grades to fill an array that contains 12 elements.

i know i need like
CLS
DIM grades(1000)
then im lost. i would madly appreciate if somebody who knows qbasic would give me a hand.