what could cause a production volume variance for fixed expenses?

a$.$ The number of units actually sold is different that the units upon which the static budget was based

b$.$ Insurance cost on the factory rise unexpectedly during the year due to a crisis in the insurance industry

c$.$ The lease on the manufacturing facility is renegotiated and the lease payments increase during the year

d$.$ The union calls for a strike of factory workers and temporary workers are hired to fill in for the striking employees