Annuity problem? Please Help!

Matthew deposits $150 each month in his account for 10 years. How much would he have after the 10 year period if the bank pays 6% p.a. interest compounded on a half yearly basis? (Sow all Working)

Heres what i got so far . . .

150 x { (1 + 0.03) to the power of 120 - 1 }

------------------------------------------ =

0.03

But i'm not sure if i get the right answer . . .

do i half the interest rate to 0.03?

and do I put 120 time periods for ( 10 years x 12 months) the amount of deposits or 20 time periods for (10 years x 2 = 20 half years) . . . ?

Thankyou if you help or for trying to help . . . i gtg to bed so yeah (Yawn) someone please be really smart on right now . . . .