(a) In an action to which Chapter 33 applies, the court shall instruct the finder of fact regarding the determination of responsibility pursuant to Section 33.003 using the appropriate approved pattern jury charge which may be modified by the court as appropriate to the circumstances.
(b) In all actions not governed by Subsection (a), the court shall instruct the finder of fact regarding a claimant's duty to mitigate or avoid damages in a manner appropriate to the action using the appropriate approved pattern jury charge which may be modified by the court as appropriate to the circumstances.