A 90′ x 40′ wide x 4′ deep hole is excavated in unstable wet clay with a 30′ boom. Which piece of equipment would do the job with the least number of position changes?

A 90′ x 40′ wide x 4′ deep hole is excavated in unstable wet clay with a 30′ boom. Which piece of equipment would do the job with the least number of position changes?