help with math question

Question

• determine an accurate figure for the labour element ( labour hours per tonne) for fixing of (a) 10 mm, and (b) 16 mm reinforcing bar ( which, together , make reinforcement cages for the unit).it is a well established fact that the labour rate for fixing reinforce bars depends on the diameters of bar being fixed ; the small bar ,more labour hours per tonne .the labours are also related to the complexity of the work .the problem here is , as in most cases , a steels fixer will fix different diameters of bar at the same time . however, it is relatively easy if proper records are kept ,to measure the total hours against the tonnage fixed . so, to determine this , assume you have looked at some previous records ( past productions figure and timesheets) as given below.
  First month:
  12.0tonnes of 16 mm diameter and 8.0 tonnes of 10 mm diameter fixed in a total of 389 labour hours.
  Second months:
  9.7 tonnes of 16 mm diameter and 6.9 tonnes of 10 mm diameter in the total 325 labours hours .
  Thank you in advance.