A Floating Leaf Bobs Up and Down Two Complete Cycles $10 \mathrm {~m} / \mathrm { s }$

A floating leaf bobs up and down two complete cycles each second as water waves pass by five meters apart. How fast are the waves moving? a. $10 \mathrm {~m} / \mathrm { s }$

b. $20 \mathrm {~m} / \mathrm { s }$

c. $30 \mathrm {~m} / \mathrm { s }$

d. $40 \mathrm {~m} / \mathrm { s }$