Situation $6.$ A $10-mm$ thick steel pipe with inside diameter of $600mm$ conveys water under a head of $480m.$

What is the tensile stress in the pipe in MPa $?$

a$.156\mathrm{.}8$

b$.141\mathrm{.}3$

c$.132\mathrm{.}1$

d$.187\mathrm{.}4$

What is the stress in the pipe wall if the head is increased to $500m$ of water?

a$.163\mathrm{.}9$MPa

b$.147\mathrm{.}15$MPa

c$.118\mathrm{.}7$MPa

d$.163\mathrm{.}3$MPa

What is the required thickness under a head of $500m$ if the allowable tensile stress of the pipe is $118$

MPa and assuming that the joints are $80\%$ efficient.

a$.21\mathrm{.}4mm$

b$.12\mathrm{.}2mm$

c$.15\mathrm{.}6mm$

d$.18\mathrm{.}9mm$