We know that there are 900units in 1 production run. Now we want to know about the total units. we can get from the given data like that
100orders* 60units + 60orders*50units =9000 units
to get the RUNS 9000/900 = 10 runs
100orders* 60units + 60orders*50units =9000 units
to get the RUNS 9000/900 = 10 runs