Paloma likes to talk on the phone. We can represent her preferences with the utility function U (R, J) = 4R + 16J, where R and J are minutes of conversation per month with Rajan and J akub respectively. What is the formula for her indifference curve to get U units of utility (that is, at utility of U, write the formula for an indifference curve with J on the vertical axis and R on the horizontal axis)? What is her marginal rate of substitution of minutes talking to Rajan for minutes talking to J akub