In this case the pedal cranks are $170$ mm long which is the most common crank length

for people of average height. You are considering changing the pedal cranks to either the shorter

$165$ mm option $($for shorter people$)$ or the longer $175$ mm option $($for taller people$).$ Which one will

increase the linkage effectiveness when the pedal cranks are horizontal? If you can$$t afford the

new cranks, what else can you do to increase the linkage effectiveness in this case