The values in Rule Strength table.

$M_{MD} \ ^{(x)} \cap M_{MG} \ ^{(y)} = \frac{3}{5}$

$M_{MD} \ (x) \cap M_{2G} \ ^{(y)} = \frac{2}{5}$

$M_{LD} \ (x) \cap M_{mG} \ ^{(y)} = \frac{1}{5}$

$M_{LD} \ (x) \cap M_{LG} \ ^{(y)} = \frac{1}{5}$

Max of all the above four value is

$M_{MD} \ ^{(x)} \cap M_{mG} \ ^{(y)} = \frac{3}{5}$

So $M_{Wash \ Time} \ ^{(z)} = \frac{3}{5}$

$\therefore$ $M_{wash \ Time} \ ^{(z)} = \frac{z – 10}{15}$

$\frac{40 – z}{15}$

$\frac{z – 10}{15} = \frac{3}{5}$

$\frac{40 – z}{15} = \frac{3}{5}$

= 31

$Z^* = \frac{z_1 + z_2}{2} = \frac{19 + 31}{2} = 25 \ mins$