Figure $27-5.$ The figure shows a utility function for Dexter. Figure $27-5.$ The figure shows a utility function for Dexter.

Refer to Figure $27-5.$ In what way$($s$)$ does the graph differ from the usual case?

a$.$ On the graph shown here, utility is measured along the vertical axis, whereas in the usual case satisfaction is measured along the vertical axis.

b$.$ On the graph shown here, wealth is measured along the horizontal axis, whereas in the usual case saving is measured along the horizontal axis.

c$.$ The utility function shown here is upward$-$sloping, whereas in the usual case the utility function is downward$-$sloping.

d$.$ The utility function shown here is bowed downward $($convex$),$ whereas in the usual case the utility function is bowed upward $($concave$).$