`$1200.00`

Let the sum invested be **a**

If **a** had been invested at 3% more interest then it would have earned $72.00 more for 2years.

So, the 3% of the amount **a** invested for 2 yrs = $72.00, so interest for 1yr = $36.00

Now,

**a** * 3% = $36.00

so, **a** = $36.00/3%

thus,

**a** = **$1200.00**

Thus, the money put on interest is $1200.00