A glass containing water has two holes. The 1st hole alone empties the glass in 9 minutes and 2nd hole alone empties the glass in 3 minutes. If water leaks out at a constant rate, how many minutes will it take if both the holes together empty the glass?

A

$$\frac{1}{4}$$

B

$$2\frac{2}{4}$$

C

$$3\frac{1}{4}$$

D

$$2\frac{1}{4}$$