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Hard chemistry question help

Help please! I have no idea how to do this. The answer is 2.6 MJ - How??

10Al(s) + 6NH4ClO4(s) 4Al2O3(s) + 2AlCl3(s) + 12H2O(l) + 3N2(g)
Enthalpy change = -9769 kJ mol-1
Given that 450 tonnes of solid propellant are used in the solid rocket boosters in total, and that aluminium is the limiting reagent present at 16% in the mixture, calculate the energy released when this is reacted according to the above equation.
When you say
Enthalpy change = -9769 kJ mol-1
That is very ambiguous. The unit is kJ per mole, but per mole of what? Of Aluminium? Of AP?
Similarily, when you say
present at 16% in the mixture
Does that mean 16% in terms of mass? In terms of quantity? In terms of volume?
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weird tricky question this typical Olympiad vague

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