As far hack as the 16th century, South American Incas chewed the leaves 01 the coca bush,

Question:

As far hack as the 16th century, South American Incas chewed the leaves 01 the coca bush, Erythroxylon coca, to combat fatigue. Chemical studies of Erythroxylon coca by Friedrich Wohler in 1862 resulted in the discovery of cocaine, C17H21NO4, as the active component. Basic hydrolysis of cocaine leads to methanol, benzoic acid, and another compound called ecgonine, C9H15NO3. Oxidation of ecgonine with CrO3 yields a keto acid that readily loses CO2 on heating, giving tropinone.

(a) What is a likely structure for the keto acid?

(b) What is a likely structure for ecgonine, neglecting stereochemistry?