`1 L` of a gaseous mixture is effused in `5 min 11s`, while `1 L` of oxygen takes `10 min`. The gaseous mixture contains methane and hydrogen. Calculate
(`a`) The density of gaseous mixture.
(`b`) The percentage by volume of each gas in mixture.

Explanation

To solve the problem step by step, we will follow the principles of Graham's law of diffusion and the relationships between density, molar mass, and effusion rates.

### Step-by-Step Solution

**Step 1: Convert Time to Seconds**
- Convert the time taken for effusion of both the gaseous mixture and oxygen into seconds.

For oxygen:
...