Wake County has a special emergency rescue team. The team is practicing rescuing dummies from a smokefilled building. The first time, the team took $180$ seconds $(3$ minutes$).$ The second time, it took $144$ seconds $(2\mathrm{.}4$ minutes$).$

Click the icon to view the learning curves table.

a$.$ The estimated learning rate is

$\%.($Enter your response as a whole number.$)$