Lucy and Martha left the Central Market and went to the Botanic Garden, where both agreed to follow the same path. The two left the Central Market at the same time, but Lucy was riding her bike, while Martha was walking. Lucy's speed was four times larger than Martha's speed, and both of them had constant speed. Lucy arrived at the Botanic Garden, waited for 5 minutes and then returned the same way, finding Martha halfway between the Botanic Garden and the Central Market.

How long does it take for Martha to walk from the Central Market to the Botanic Garden?