There are three workers Ram, Tom and Jill who take 3 hour. 2 hours and 4 hours respectively, for manufacturing a toy by themselves. How long would it take if all three workers worked together. (in hours)

A

$$\frac{13}{12}$$

B

$$\frac{12}{13}$$

C

$$\frac{13}{11}$$

D

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