||4. The demand for pencils by Ramapo students at the bookstore is given by the following equation, pencils = 100-.11 -10Ppexis, where I is the average income of Ramapo College students, in dollars per week, pencils is the quantity of pencils sold per week, and Ppencils is the price per pencil, in dollars. Last week, the average income of Ramapo students was $100 per week and the bookstore sold pencils for $1 each. (5 points each) a. What was the price elasticity of demand last week? b. Find what income elasticity of demand was last week.