Automatic generation of Mark distribution

I need to automate the mark distribution based on each lesson with the below conditions:

N6 to N13 should always be 16 marks and marks should be distributed for that corresponding row which will add up to 16 marks (* Marks per question varies for each question type and i have mentioned it in the column name):

Rule 1: B6:M6 to add up to 16 marks with the following conditions:

if G6 has an input then H6 must be blank and vice versa..

similarly same Rule 1 applies for G7,H7, .....G13,H13.

Rule 2: For column K, from lesson 1 to 4 one random entry and lesson 4 to 8 one random entry.

similarly Rule 2 applies for column L.

The above two rules must satisfy the rule 3.

Rule 3: For column B15:M15 i have already used conditional formatting which turns green when the right number of questions are chosen.