Percentage of silver in German silver is (in $\%$)

For the following statements,mark $T$ for true and $F$ for false statement.
Statement $1$: $SnO_2 +$ wolframite,in this $SnO_2$ is magnetic while wolframite is non-magnetic in nature.
Statement $2$: Argentite ore is concentrated by froth floatation method.
Statement $3$: Copper and lead ores are reduced by self-reduction method.
Statement $4$: In metallurgy of $Fe$,$CO$ is used as a reducing agent at low temperature.

Identify the products of the reaction: $4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \rightarrow ?$

Which of the following statements is wrong?

Which of the following metals is present in Brass,Bronze,and German silver?

Brass is an alloy of copper and ......... .