Sum column cells across multiple colums

Hello,

I have a table in excel, series of columns with Prices per weight and then each row shows someones post usage and quantity per weight band.

what im trying to do is, put a formula in so that at the end of the row, display the sections combined postage.

Tried a few different variations but cant find an automatic way to create a formula rather than doing a long manual one i.e =E5*E7+F5*F7+G5*G7+H5*H7+I5*I7+J5 all the way to BN

The next row down would then be the same price row (4) and quantity row change from 5 to 6. Thoguht if i had one that worked , could just autofill down so that the row changed to 7,8,9 etc.

Thought I was on the right lines like this but obviously not

SUM(MMULT(E3:E5,H3:H5))

SUMPRODUCT(E3:E5,H1:H5)

Ive adjusted the references to suit my colums, doesnt seem to add things up correct
Column E-I should total = £8.05
Doesnt seem to be calculating column E total and adding it in

attached the page im working on with the formula. i managed to get it working where i can autofill it down for other rows, they add up the first calculation ok. just E5 doesnt work