Use this phase diagram for the next two questions.

$Cu-Ni$ phase liagram

tdapted from Fig. $9\mathrm{.}3($a$),$ Callister & Rethwisch $8$e$.($Fig$.9\mathrm{.}3($a$)$ is adapted from Jhase Diagrams of Binary Nickel Alloys, J$.$ Nash $($Ed$.),$ ASM International, Uaterials Park, OH $(1991).$

a$.$ Using the $Cu-Ni$ phase diagram above, how many phases are present at $1800C$ and $25$ wt$\%$ Cu$?$

i$.0$

ii$.1$

iii. $2$

iv$.3$

b$.$ What are the compositions of each of the phases present at $1350C$ and $65wt\%Ni?$

i$.$ L: $20wt\%Ni,$:$32wt\%Ni$

ii$.$ L: $32wt\%Ni,$:$20wt\%Ni$

iii. L: $32wt\%Ni,$:$60wt\%Ni$

iv$.$ L: $60wt\%Ni,$:$32wt\%Ni$

v$.$ L: $60wt\%Ni,$:$72wt\%Ni$

vi$.$ L: $72wt\%Ni,$:$60wt\%Ni$

vii. The test is wrong, the professor made a mistake.