1. One more question on solids in physics, On bone and enamel in teeth. The unit cell (or half of it)can be accessed in Wikipedia for the calcium hydroxyapatite crystal

structure of bone whoseformula is Ca10(PO4)6(OH)2. From Wikipedia: Hydroxyapatite, alsocalled hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with theformula Cas(PO.)>(OH), but it is usually written Ca0(PO.)6(OH)2 to denote that the crystal unitcell comprises two entities. The following resource is from the national institutes: а.How many OH-1 units are in the full unit cell? b.Answer how fluoride strengthen teeth enamel and C.what portion of the unit cell of the bone mineral it replaces. d. Here is half the unit cell. Give its formula [key: green- Ca, orange- P, red- O, and white- H]