Please show the working .·´¯`(>▂<)´¯`·. [microscopy and measuring cells]

Q] An eyepiece graticule has a scale with 100 divisions. A stage micrometre has a scale with 50 divisions, each of which is 0.040 mm apart. Using a 40X objective lens, the whole length of this stage micrometre scale lines up with 15 divisions of the eyepiece graticule. What is the actual length of the 100 division scale of the eyepiece graticule?

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.