How to sum cells by condition in another cell?

Question

Google Sheets

Good afternoon!
I can't write the formula.
Example:
If in column "a" after an integer there are fractional numbers (for example, 3 and after it 3.1), then the numbers in column "c" should be summed up in a column with an integer.
Example in screenshots:
What is -

What is needed -

Answer 1

Just add the condition you described in the question.
=IF(AND(A1<>"";INT(A1)-A1=0);B1*D1;"")

Answer 2

A7 / WHOLE(A7) = 1
A8 / WHOLE(A8) ≠ 1
Got it?