Durant is a leading manufacturer of armored vehicles for the U$.$S$.$ Armed Forces. Durant has been able to secure many contracts because of its use of duranium, a rare metal that is difficult to locate and extract. Currently only one company, Minekraft, mines and supplies duranium. According to Porter$$s Five$-$Forces model for industry analysis, which force should Durant be most concerned with regarding Minekraft?

a$.$

Threat of new entrants

b$.$

Threat of substitute products and services

c$.$

Bargaining power of suppliers

d$.$

Rivalry among competitors

e$.$

Threat of low resource allocation

f$.$

Bargaining power of buyers