If I'm correct the answer should be a series circuit :) Hopefully this helps you out
Lets let our mass equal 3 on alletals and solve using d=m/v equation
Aluminum
V=3/2.70=1.11
Silver
V=3/10.5=.286
Rhenium
V=3/20.8=.144
Nickel
V=3/8.90=.337
This gives us the following list from largest to smallest Aluminum, Nickel, Silver, and Rhenium