JEE Advanced 2025 · Paper 2, Mathematics question 11

A factory has a total of three manufacturing units, $M_1$, $M_2$, and $M_3$, which produce bulbs independent of each other. The units $M_1$, $M_2$, and $M_3$ produce bulbs in the proportions of $2 : 2 : 1$, respectively. It is known that 20% of the bulbs produced in the factory are defective. It is also known that, of all the bulbs produced by $M_1$, 15% are defective. Suppose that, if a randomly chosen bulb produced in the factory is found to be defective, the probability that it was produced by $M_2$ is $\dfrac25$.

If a bulb is chosen randomly from the bulbs produced by $M_3$, then the probability that it is defective is _____.