They are correct? thank you!

In which phase does software coding and testing happen in the spiral model? the spiral model does not have a separate testing phase. both, software coding and testing occurs during the phase.

Jane’s team is using the v-shaped model for their project. during the high-level design phase of the project, testers perform integration testing. what is the purpose of an integration test plan in the v-model of development? a. checks if the team has gathered all the requirements b. checks how the product interacts with external systems c. checks the flow of data in internal modules d. checks how the product works from the client side

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?