Explanation:
In the parallel combination, the equivalent resistance is given by :

4. When three 150 ohms resistors are connected in parallel, the equivalent is given by :

5. Three resistors of 20 ohms, 40 ohms and 100 ohms are connected in parallel, So,

Hence, this is the required solution.
C.figure 3 is the answer had the same and got is right
1.8 mol of Na. hope this helps