Study the given pattern carefully and select the number that can replace the question mark (?) in it.
First row - 6, 9, 90
Second row - 12, 8, 120
Third row - 13, 6, ?
(NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 - Operations on 13 such as adding / subtracting / multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is NOT allowed)