When a gas expands along $AB($see below$),$ it does $20J$ of work and absorbs $30J$ of heat.

When the gas expands along $AC,$ it does $40J$ of work and absorbs $70J$ of heat. $($a$)$ How

much heat does the gas exchange along $BC?($b$)$ When the gas makes the transition from

$C$ to A along CDA, $60J$ of work are done on it from $C$ to D$.$ How much heat does it

exchange along CDA?