50 mL of each gas A and of gas B takes 200 and 150 s respectively for effusing through a pinhole under the similar conditions. If the molecular mass of gas B is 36, the molecular mass of gas A will be:

1. 96

2. 128

3. 32

4. 64

A certain gas takes three times as long to effuse out as helium. Its molecular mass will be:

1.  36 u
2.  64 u
3.  9 u
4.  27 u