[Builds from Q3(a) and Q3(b)]

The SuperSlow car factory, located in the next town over, is similar to the QuickFast car factory in many respects. However, employees at the SuperSlow car factory do not have a retirement pension. On average, 64 year old employees of the SuperSlow car factory work 300 days per year, and 66 year old employees of the SuperSlow car factory work 225 days per year. Using this information, construct a difference-in-differences estimate of the effect of retirement pensions on labour supply.