Glasbrook Brothers v Glamorgan (modified) with facts as follows

At a time of industrial unrest, coal mine owners negotiated with the Police Department and agreed to pay for a "special guard" on the mine. Later they denied liability saying that the poice had done no more than perform their existing public duty of maintaining order. The police in fact occupied the interior recesses of the mine.

[a] To answer whether the promise of the coal mine owners is enforceable, which rule must be applied? (Rule must be based on consideration theory. Otherwise, zero marks will be awarded for the whole question set.)

[b] Using that rule, is the promise enforceable? Answer YES or NO and explain making reference to relevant theory.

[c] Which precedential case can you cite in relation to question [b] above that is dispositive? Cite the name of that case.