To find out how much Rob paid per share when he bought the stock two years ago, we need to calculate \(\frac{3}{4}\) of the current price.
The current price per share is $19.80.
Now, we calculate: \[ \text{Price at purchase} = \frac{3}{4} \times 19.80 \]
Calculating this: \[ \frac{3}{4} \times 19.80 = \frac{3 \times 19.80}{4} = \frac{59.4}{4} = 14.85 \]
Thus, Rob paid \(\boxed{14.85}\) per share when he bought the stock two years ago.