On March 11, 2020, the World Health Organization (WHO) declared COVID-19 to be a global pandemic. In that month, the demand for hand sanitizer increased and supply could not initially keep up, leading to price increases. Please include a figure with a short explanation.

a) For the firms producing hand sanitizer, did their marginal costs change as they tried to produce more sanitizer? If so, how? Again, show this with a figure.