Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Let me give you an example: In 1582 the united provinces invited francis, duke of anjou to lead them; but after a failed attempt to take antwerp in 1583, the duke left the netherlands again. after the assassination of william of orange (10 july 1584), both henry iii of france and elizabeth i of england declined the offer of sovereignty. however, the latter agreed to turn the united provinces into a protectorate of england (treaty of nonsuch, 1585), and sent the earl of leicester as governor-general. this was unsuccessful and in 1588 the provinces became a confederacy. the union of utrecht is regarded as the foundation of the republic of the seven united provinces, which was not recognized by the spanish empire until the peace of westphalia in 1648.
The answer to this example can be: In what year did francis, duke of anjou leave the netherlands?
Here is why: The generated question is perfect. Because the question is based on second sentence of the input passage and its answer is 1583.

OK. solve this:
Somatic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene are present in lung adenocarcinomas that respond to the EGFR inhibitors gefitinib and erlotinib. Two types of mutations account for approximately 90% of mutated cases: short in-frame deletions in exon 19 and a specific point mutation in exon 21 at codon 858 (L858R). Screening for these mutations has been based mainly on direct sequencing. We report here the development and validation of polymerase chain reaction-based assays for these two predominant types of EGFR mutations. The assay for exon 19 mutations is based on length analysis of fluorescently labeled polymerase chain reaction products, and the assay for the exon 21 L858R mutation is based on a new Sau96I restriction site created by this mutation. Using serial dilutions of DNAs from lung cancer cell lines harboring either exon 19 or 21 mutations, we detected these mutations in the presence of up to approximately 90% normal DNA. In a test set of 39 lung cancer samples, direct sequencing detected mutations in 25 cases whereas our assays were positive in 29 cases, including 4 cases in which mutations were not apparent by sequencing. These assays offer higher sensitivity and ease of scoring and eliminate the need for sequencing, providing a robust and accessible approach to the rapid identification of most lung cancer patients likely to respond to EGFR inhibitors.
Answer:
Mutations in which gene determine response to both erlotinib and gefitinib?