I have an array of numbers like
100 0.01
200 0.015
300 0.02
400 0.025
500 0.03

say the range name is tab1

and an array of numbers like (call it tab2)
150
250
350
I want to look up the numbers from tab2 in tab1 and multilply it by the 2nd
column from tab1 and add up the result.
So, I want 150*.01+250*.015+350*.02

I tried as an array formula =sum((vlookup(tab2,tab1,2)*tab2)
but this does not work.
What should I be doing?

TIA