Describe two potential problems that should be avoided in relevant$-$cost analysis.

Choice $1$ of $4$:$($i$)$ Focusing on total revenues and total costs $($rather than unit revenue and unit cost$).($ii$)$ Focusing on the relevance concept.Choice $2$ of $4$:$($i$)$ Assuming that all variable costs are relevant and all fixed costs are irrelevant. $($ii$)$ Using unit$-$cost data directly.Choice $3$ of $4$:$($i$)$ Focusing on the relevance concept. $($ii$)$ Using total cost data directly.Choice $4$ of $4$:$($i$)$ Focusing on total revenues and total costs $($rather than unit revenue and unit cost$).($ii$)$ Using unit$-$cost data directly.