CREATE TABLE table_name_91 (ceased_to_be_duke_of_girona VARCHAR2, heir_of VARCHAR2)

WHAT IS THE Ceased to be Duke of Girona THAT HAS PETER IV?
SELECT ceased_to_be_duke_of_girona FROM table_name_91 WHERE heir_of = "peter iv"
SELECT "ceased_to_be_duke_of_girona" FROM "table_name_91" WHERE "heir_of" = "peter iv"