Which is the correct decreasing order of basic strength in water of (I) $(\mathrm{C}{}_2\mathrm{H}{}_5){}_2\mathrm{NH}$, (II) $(\mathrm{C}{}_2\mathrm{H}{}_5){}_3\mathrm{N}$, (III) $\mathrm{C}{}_2\mathrm{H}{}_5\mathrm{NH}{}_2$, (IV) $\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{NH}{}_2$ and (V) $\mathrm{CH}{}_3\mathrm{CONH}{}_2$?

For the ethylamines the aqueous order is $(\mathrm{C}{}_2\mathrm{H}{}_5){}_2\mathrm{NH}>(\mathrm{C}{}_2\mathrm{H}{}_5){}_3\mathrm{N}>\mathrm{C}{}_2\mathrm{H}{}_5\mathrm{NH}{}_2$ (inductive effect balanced by solvation and steric factors). Aniline is far weaker than any alkylamine because of lone-pair delocalisation into the ring. Acetamide is weaker still because its lone pair is delocalised onto the carbonyl oxygen (essentially neutral in water).