2. Decimal Strings A dec-string is a sequence of characters from the 10-character alphabet {0,1,2,3,4,5,6,7,8,9}. For example, these are dec-strings: 36562342320 49548362729 Let n > O be an integer. 7. A dec-string d,..., dn is bad if di =di+1 or d; +di+1 = 9 for at least one i e{1,...,n-1} and it is good otherwise. What is the number of good dec- strings of length n? 8. A dec-string d1, ..., dn is 2-bad if di = d; or di +d;=9 for some i O be an integer. 7. A dec-string d,..., dn is bad if di =di+1 or d; +di+1 = 9 for at least one i e{1,...,n-1} and it is good otherwise. What is the number of good dec- strings of length n? 8. A dec-string d1, ..., dn is 2-bad if di = d; or di +d;=9 for some i