Two crates are connected by a massless rope that passes over a pulley as shown in Figure...

Two crates are connected by a massless rope that passes over a pulley as shown in Figure 4.26. If the crates have mass 35 kg and 85 kg, what is their acceleration? If the system begins at rest, with the more massive crate a distance 12 m above the floor, how long does it take the more massive crate to reach the floor? Assume the pulley is massless and frictionless.

(reference figure 4.26)