The demand of a product is known to vary with the price of the product. The price was varied to take $6$ different values on $6$ consectuive days. The price over the six days was $10,12,13,12,16$ and $15$ respectively; while the demand was found to be $40,38,43,45,37$ and $43$ units respectively. The expected demand of the product at the price of INR $24$ is $....$ units. The demand of this product is likely to $....$ by $.....$ units for a unit increase in the price.

a$.38\mathrm{.}5,$ decrease, $0\mathrm{.}5$

b$.38,$ decrease, $1$

c$.38\mathrm{.}25,$ decrease, $0\mathrm{.}25$

d$.38\mathrm{.}75,$ increase, $0\mathrm{.}5$