True or false
a)elasticity of demand measures the ratio of percentage change in quantity demanded to percentage change in income.
b)sales of the common necessities of life tend to increase sharply where there is a drop in their prices.
c)a straight-line demand curve, unless vertical or horizontal, does not have constant elasticity at every point.
d)a perfectly elastic supply curve must be a vertical line.
e) an increase in supply price most when demand is elastic and decrease it least when demand is relatively inelastic.