One of your parameters is called "c2" and does not appear in the formula. Rename it to "c"
The array of parameters has 4 elements, the last element being an emtpy string. (resize the container to see all, the size of the container does not determine the size of the array!) You need to remove that fourth array element.
(Besides, I don't think any of your flat sequence structures are necessary, they just clutter up the diagram).