In the notation $$(a/b/c) : (d/e/f)$$ for summarizing the characteristics of queuing situation, the letters $$‘b’$$ and $$‘d’$$ stand respectively for

For the linear programming problem:
$$\eqalign{ & Maximize\,\,\,\,\,Z = 3{x_1} + 2{x_2} \cr & Subject\,\,to\,\,\,\, - 2{x_1} + 3{x_2} \le 9 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{x_1} - 5{x_2} \ge - 20 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{x_1},\,\,{x_2} \ge 0 \cr} $$

The above problem has

For ball bearings, the fatigue life $$L$$ measured in number of revolutions and the radial load $$F$$ are related by $$F{L^{1/3}} = K,$$ where $$K$$ is a constant. It withstands a radial load of $$2$$ $$kN$$ for a life of $$540$$ million revolutions. The load (in $$kN$$) for a life of one million revolutions is ___________.

A cantilever bracket is bolted to a column using three $$M12 \times 1.75$$ bolts $$P, Q$$ and $$R.$$ The value of maximum shear stress developed in the bolt $$P$$ (in $$MPa$$) is _______________.