$2\mathrm{.}6\mathrm{.}27$ The cistern shown in Fig. P$2\mathrm{.}6\mathrm{.}27$ has a diameter $D$ that is four

times the diameter $d$ of the inclined tube. Find the drop in the fluid

level in the cistern and the pressure difference $(p_A-p_B),$ if the liquid

in the inclined tube rises $l=0\mathrm{.}51m.$ The angle $$ is $20.$ The fluid's

specific gravity is $0\mathrm{.}85.$

FIGURE P$2\mathrm{.}6\mathrm{.}27$