Identify the type of code used by a trading company Ms. Ahana Ltd.:
| Codes | Accounts |
| CA005 | Super Ltd. |
| CA006 | Regina Ltd. |
| CA007 | Nasir & Sons Ltd. |
Study the given molecular structure of double-stranded polynucleotide chain of DNA and answer the questions that follow. 
(a) How many phosphodiester bonds are present in the given double-stranded polynucleotide chain?
(b) How many base pairs are there in each helical turn of double helix structure of DNA? Also write the distance between a base pair in a helix.
(c) In addition to H-bonds, what confers additional stability to the helical structure of DNA?